• 한국강구조학회 논문집
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• 제25권3호
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• pp.223-231
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• 2013

최근 구조물의 고층화, 대형화 및 장스팬 활용 등의 요구로 고강도 고성능 재료의 건축물과 교량에의 적용이 증가하는 추세이다. 본 논문은 고성능강(HSA800)의 건축구조용 재료 특성과 고성능강재를 사용한 부재의 설계 기준을 위한 기본적인 연구의 일부이다. 조립각형강관 기둥의 국부좌굴 거동과 현행 폭두께비 설계 제한치를 검토하기 위하여 다양한 폭두께비 변수를 계획하고, 단축압축실험을 실시하였다. 또한, 유한요소결과로 얻어낸 단주의 국부좌굴거동을 실험결과와 비교하였으며 검증된 해석모델을 이용하여 변수연구를 수행하였고 현행 설계기준의 적용성에 대해 검토하였다.

• Steel and Composite Structures
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• 제24권5호
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• pp.537-548
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• 2017

In this paper presents bending characteristic of single wall carbon nanotube reinforced functionally graded composite (SWCNTRC-FG) plates. The finite element implementation of bending analysis of laminated composite plate via well-established higher order shear deformation theory (HSDT). A seven degree of freedom and $C^0$ continuity finite element model using eight noded isoperimetric elements is developed for precise computation of deflection and stresses of SWCNTRC plate subjected to sinusoidal transverse load. The finite element implementation is carried out through a finite element code developed in MATLAB. The results obtained by present approach are compared with the results available in the literatures. The effective material properties of the laminated SWCNTRC plate are used by Mori-Tanaka method. Numerical results have been obtained with different parameters, width-to-thickness ratio (a/h), stress distribution profile along thickness direction, different SWCNTRC-FG plate, boundary condition, through the thickness (z/h) ratio, volume fraction of SWCNT.

• 조명전기설비학회논문지
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• 제28권5호
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• pp.39-51
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• 2014

This paper deals with design of a direct-coupled, small-scaled permanent magnet generator (PMG) for wind power application. First, this paper determines rated power and speed of the PMG from measured characteristics of wind turbines. Second, we derive analytical solutions for the open-circuit field in order to determine optimum magnet thickness and pole pitch/arc ratio. Third, on the basis of open circuit field solutions, stator magnetic circuit including slot opening, teeth width and yoke thickness is designed. And then, a diameter of stator coil which agree with a required current density is calculated, and its turns are determined from the area of slot considering winding packing factor. Finally, finite element (FE) method is employed in analyzing the details of the designed PMG and, test results such as back-emf measurements are given to confirm the design.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.413-414
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• 2008

We have studied an organic layer thickness dependent optical properties and microcavity effects for top-emission organic light-emitting diodes. Manufactured top emission device, structure is Al(100nm)ITPD(xnm)/$Alq_3$(ynm)/LiF(0.5nm)/Al(23nm). While a thickness of hole-transport layer of TPD was varied from 35 to 65nm, an emissive layer thickness of $Alq_3$ was varied from 50 to 100nm for two devices. A ratio of those two layers was kept to about 2:3. Variation of the layer thickness changes a traverse time of injected carriers across the organic layer, so that it may affect on the chance of probability of exciton formation. View-angle dependent emission spectra were measured for the optical measurements. Top-emission devices show that the emission peak wavelength shifts to longer wavelength as the organic layer thickness increases. For instance, it shifts from 490 to 555nm in the thickness range that we used. View-angle dependent emission spectra show that the emission intensity decreases as the view-angle increases. The organic layer thickness-dependent emission spectra show that the full width at half maximum decreases as the organic layer thickness increases. Top emission devices show that the full width at half maximum changes from 90 to 35nm as the organic layer thickness increases. In top-emission device, the microcavity effect is more vivid as the organic layer thickness increases.

• Advances in environmental research
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• 제5권3호
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• pp.201-211
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• 2016

Laboratory tests were conducted to evaluate the performance of waste rubber shreds in leachate collection layer of engineered landfills. The study found that waste rubber shreds layer in combination with a gravel layer can be of potential use in landfill drainage system. To study the performance, conventional gravel along with waste rubber shreds were used in different combinations (with total layer thickness = 500 mm) as leachate collection media. For the laboratory study poly vinyl chloride (PVC) pipes were used. The size range of waste rubber shreds used were 25 mm to 75 mm in length and width = 10 to 20 mm. The gravel size used in the leachate collection media is 10 mm to 20 mm size. Performance study of 7 Test Cols. with different combinations of waste rubber shreds and gravel bed thickness were studied to find out the best combination. The study found that the Test Col.-3 having waste rubber shreds thickness = 200 mm and gravel layer thickness = 300 mm gave the best results in terms of percentage removal in various physicochemical parameters present in the leachate. Further to find the best size rubber shreds three more Test Cols - 8, 9 and 10 were constructed having the rubber shreds and gravel layer ratio same as that of Test Col.-3 but having rubber shreds width = 10 mm, 15 mm and 20 mm respectively. Based on the results obtained using Test Cols. 8, 9 and 10 the study found that smaller size rubber shreds gave bests results in terms of improvement in various leachate parameters.

• 한국산학기술학회논문지
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• 제22권2호
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• pp.617-624
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• 2021

각형강관 기둥에 콘크리트를 충전하여 사용하는 콘크리트충전 강관구조가 구조부재로 사용되면 기둥 부재의 내력과 변형 능력이 증가되어 높은 효율성을 가진 구조물 구현이 가능해 진다. 콘크리트충전 강관구조에 대한 국내의 설계 기준은 대한건축학회에서 2005년에 제정한 후, 2009년과 2016년에 각각 개정되었다. 연구 목적은 콘크리트충전 각형강관 단주를 대상으로 일축 압축실험을 실시하여 압축내력 및 변형능력에 주는 영향을 파악하고, 국내의 건축구조기준의 기준식을 검증하여 차후 수정 및 보완에 필요한 자료를 제공하는데 있다. 실험에서 강관은 냉간가공으로 제작된 각형강관을 사용하였고, 시험체는 강관의 폭두께비를 변수로 총 26개를 제작하여 중심 압축실험을 실시하였다. 실험결과 콘크리트충전 각형강관 단주의 압축내력과 변위관계 및 파괴모드를 얻었고, 실험결과를 분석하여 콘크리트의 충전효과와 폭두께비의 영향을 파악하였다. 충전된 콘크리트의 압축내력은 일축응력 상태보다 9%정도 증가하였는데, 이것은 차후 건축구조기준에 반영할 필요가 있다. 실험결과를 건축구조기준과 비교한 결과, 냉간가공된 각형강관의 경우 건축구조기준의 콤팩트단면 한계폭두께비 2.26은 다소 과대 평가하고 있기 때문에 수정이 필요하며, 보수적으로 보완한 계수 1.35로 제한하여 보다 더 안정적인 설계식을 제안하였다.

• Steel and Composite Structures
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• 제17권4호
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• pp.517-533
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• 2014

Experimental results of 39 specimens including concrete columns, RC columns, hollow steel tube columns, concrete filled steel tubular (CFT) columns, and reinforced concrete filled steel tubular (RCFT) columns are presented. Based on the experimental results, the load-carrying capacity, confined effect, ductility, and failure mode of test columns are investigated. The effects of the main factors such as width-thickness ratio (the ratio of external diameter and wall thickness for steel tubes), concrete strength, steel tube with or without rib, and arrangement of reinforcing bars on the mechanical characteristics of columns are discussed as well. The differences between CFT and RCFT are compared. As a result, it is thought that strength, rigidity and ductility of RCFT are improved; especially strength and ductility are improved after the peak of load-displacement curve.

• Transactions on Electrical and Electronic Materials
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• 제11권6호
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• pp.253-256
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• 2010

Different active layer thicknesses for zinc oxide (ZnO) bottom-contact thin-film transistors (TFTs) were fabricated with a poly-4-vinyphenol polymeric dielectric using injector type atomic layer deposition. The properties of the ZnO TFTs were influenced by the active thickness and width-to-length (W/L) ratio of the device. The threshold voltage of ZnO TFTs shifted positively as the active layer thickness decreased, while the subthreshold slope decreased. The W/L ratio of ZnO TFTs also affected the mobility and subthreshold slope. An optimized TFT structure exhibited an on-tooff current ratio of above 106 with solid saturation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.978-981
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• 2005

The vibration analysis of damped sandwich beam is conducted using finite element method. The equation of motion presented by Mead and Markus is used to formulate FEM. Also as the thickness of the core in the damped sandwich beam goes to zero, conventional beam theory based on the transformed-section method and the equation of Mead and Markus are compared. According to the change of thickness and loss factor of the core, the forced frequency response of beam is calculated and discussed. And then using the half-power band width method, the damping ratio of each mode is calculated and discussed about each case.

• 산업기술연구
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• 제34권
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• pp.45-52
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• 2014

In this paper the settlement characteristic of shallow foundation on sandy soil overlained by rigid ground was investigated by analyzing results of model tests. For model experiments, model tests were performed with sandy soils sampled from the field, changing the relative density of sandy soil and the ratio of thickness of sandy layer(H) to the width of model strip footing(B). As result of tests, settlement of sandy soils increases as the value of H/B increases, whereas it increases with relative density of soil. Bearing capacity decreases as the thickness of the sand layer relative to the footing width increases. In order to analyze the settlement characteristics of sandy ground, the results of model tests were compared with the predicted values using the empirical formulas proposed by Terzaghi, De Beer and Schmertmann. The method by De Beer was found to be in good agreements with test results.